DESCRIPTION: (Adapted From The Applicant's Abstract.) Impairment of the ability to understand conversation under difficult listening conditions, such as in highly reverberant rooms or in gatherings where several persons are talking simultaneously, affects a substantial portion of elderly individuals. This impairment may vary in severity, but only in very few cases can it be overcome by the use of currently available prosthetic devices. Attempts to alleviate this impairment have been impeded by the fact that neither the precise characteristics of the intact process in the young, nor the causes of its breakdown in the old, are currently well understood. The proposed research represents a continuation of work aimed at investigating the ability of both elderly and young individuals to understand speech under non-optimal listening conditions, i.e., perceptual separation of a speech target from simultaneously ongoing irrelevant "noise". The research has two main objectives: (1) to investigate, in elderly and in young listeners, the perceptual processes (in particular, spatial resolution and resolution of temporal fluctuations) which play a role in the separation of simultaneously presented relevant and irrelevant auditory signals; and (2) to study a group of elderly individuals over a five year period, in order to detect initial or progressive deterioration of the ability to separate simultaneous signals and to determine the correlates of this deterioration. These objectives will be achieved by testing selected groups of elderly and young individuals on standard and non-standard audiological tests as well as psychophysical tests. Spatial hearing will be assessed in a simulated free field. Multidimensional auditory performance profiles of subjects will be defined through principal component analysis and other multivariate statistical methods. The major scientific significance of the proposed study is that it will provide a more precise definition of auditory temporal and spatial processes that allow for the perceptual separation of speech and background noise and will also identify precise auditory processes affected by aging. The clinical significance of the study is that it will establish a multidimensional data base of auditory capabilities in elderly individuals with mild to moderate sensorineural hearing loss, and may identify auditory processes which, if impaired, will help predict impending deterioration of speech understanding under non-optimal listening conditions. This work will have an impact on a wide-spread impairment of verbal communication in the elderly.